groupby.js

groupby.js

const groupBy = (array, fn, last = false) => {
  const grouped = [];

  for (let index = 0; index < array.length; index += 1) {
    const element = array[index];
    const key = fn(element);
    const foundIndex = grouped.findIndex((v) => v.key === key);
    if (foundIndex === -1) {
      grouped.push({ key, value: element });
    } else if (last) {
      grouped[foundIndex].value = element;
    }
  }

  return grouped.map((v) => v.value);
};

/*
const groupedData = groupBy(inputData, (v) => format(new Date(v.date), 'yyyy-MM'));
*/